1. Field of the Invention
The present invention relates to a novel semiconductor plastic package in the form in which at least one semiconductor chip is mounted on a small-sized printed wiring board, a metal plate for the above package and a method of producing a copper-clad board for the above package. It relates particularly to a semiconductor plastic package suitable for relatively high-watt, multi-terminal and high-density semiconductor plastic packages such as a microprocessor, a micro-controller, ASIC and graphic, and a method of producing the same. The semiconductor plastic package of the present invention is used for an electronic device by mounting it on a mother board wiring board with solder balls.
2. Description of Prior Art
There are conventionally known semiconductor plastic packages such as a plastic ball grid array (P-BGA) and a plastic land grid array (P-LGA), which are structured by fixing a semiconductor chip on the upper surface of a plastic printed circuit board, bonding the semiconductor chip to a conductor circuit formed on the upper surface of the printed circuit board by wire-bonding, forming a conductor pad for connection to a mother board printed circuit board on the lower surface of the printed circuit board with a solder ball, connecting front and reverse circuit conductors with a plated through-hole and encapsulating the semiconductor chip with a resin. In the above known structure, a plated heat-diffusible through-hole to connect a semiconductor-chip-fixing metal foil on the upper surface to the lower surface is formed for diffusing heat generated in the semiconductor chip to the mother board printed circuit board.
There is a risk that moisture may be absorbed through the above through hole into a silver-powder-containing resin adhesive used for fixing a semiconductor and may cause an interlayer swelling due to heating at a time of mounting the above package on the mother board or heating when a semiconductor part is removed from the mother board, and it is called a "popcorn phenomenon" When the popcorn phenomenon takes place, the package is no longer usable in most cases, and it is required to overcome the above phenomenon to a great extent.
Further, attaining of higher functions of a semiconductor and increasing a density thereof imply an increase in the amount of heat to be generated, and the formation of only a through-hole immediately below the semiconductor chip for diffusing heat is not sufficient any more.